With the deepening of exploration and development, shale gas and tight gas reservoirs have entered the stage of scale development. Large-scale fracturing methods such as staged fracturing and volume fracturing of horizontal wells have gradually become the main technologies for the development of oil and gas fields. The existing staged fracturing technologies mainly include: an open-hole packer plus slide sleeve staged fracturing technology, a drillable bridge plug staged fracturing technology, a large-bore bridge plug staged fracturing technology, a double-seal single-pressure staged fracturing technology and a hydraulic jet staged fracturing technology, but they have certain limitations. The open-hole packer plus slide sleeve staged fracturing technology cannot realize a full bore and has a limited number of stages because a slide sleeve needs to be opened by different grades of balls and ball seats. The drillable bridge plug can perform unlimited-stage large-scale fracturing, but is long in operation period and high in cost. The large-bore bridge plug staged fracturing technology maintains a large bore of a borehole without drilling, but still cannot achieve a full bore of the borehole. The double-seal single-pressure staged fracturing technology needs to drag a pipe string, which requires operations under pressure, such that the operations are complex and the construction period is long. The hydraulic jet staged fracturing technology has limited construction sections, long construction period and limited construction scale owing to its limited wear and erosion resistance of nozzles and large throttle pressure difference.
At present, the productivities of all levels of reservoirs during the development of oil fields are different. Conventional completion technologies and tools are difficult to achieve production control of all levels of reservoirs, and there are problems such as water-gas coning. At the same time, as the increase in the years of oilfield exploitation, many oilfields gradually enter a high-water-cut period, resulting in a large gap in the nature of oil reservoirs. The conventional profile modification and deplugging technology cannot maintain the normal production requirements of a high-water-cut well. In this context, an intelligent completion technology has developed more rapidly. This intelligent completion technology can realize layered mining and borehole mining, and control the mining speeds of different levels or different boreholes without shutting down the well, resulting in the increase of the overall production effectiveness. An intelligent switching valve is a key tool in intelligent completion and is mainly used to open, close or throttle one or more reservoirs. By adjusting the pressure between reservoirs, a flow rate of fluid, etc., the functions, such as profile modification and deplugging, production control, and production process adjustment can be realized. Therefore, it is meaningful to develop an intelligent switching valve for reservoir reformation, production monitoring and control.
Among the prior arts, the Chinese patent “Casing Unlimited-stage Staged Fracturing Method” (publication No.: CN104929603A), published on Sep. 23, 2015 is involved, in which, various stages are set in sequence by using a continuous pipe to drag a repeatable setting and releasing tool, and a slide sleeve is opened through annular pressurizing to perform sand fracturing. This method requires auxiliary tools, and is complicated in operations and long in working hours.
In the China Patent “Switchable Layered Fracturing Cementing slide sleeve and Construction Method Thereof”, (Publication No.: CN104612647A), published on May 13, 2015, a bottom packer arranged on a multi-stage fracturing tool is pushed down by a coiled tubing in each reservoir, such that the bottom packer is set in an upper center tube, and a fracturing slide sleeve is then opened by the coiled tubing or by annular pressurizing. In this method, a ball seat is not required, and the number of stages for use of the slide sleeve is increased by a full bore. However, the use of the coiled tubing makes the number of stages still limited, and meanwhile the operation flows are complex and the time is long.
In the Chinese patent “Method for Unlimited-stage Staged Reformation of Horizontal Well” (publication No.: CN103437747A), published on Dec. 11, 2013, a control signal is delivered to a downhole slide sleeve through an input signal transmitter, a piston is pushed by a power mechanism to form a ball seat, and the fracturing operation is performed in a dropping-to-pressurizing manner. In this method, a ball seat is used, and the fracturing operation can be implemented in the order of stages. The formed ball seat cannot be reset, and the input ball cannot be recycled, which increases the difficulty of subsequent operations.
In the Chinese Patent “Accumulator-Driven Slide Sleeve Switch for Petroleum Completion” (publication No.: CN105019862A), published on Nov. 4, 2015, a slide sleeve is opened and closed by storing a gas having a certain pressure in a plurality of gas storage holes in a porous welding member as a power source of a hydraulic control circuit, by using a plurality of oil storage holes and oil return holes in the porous welding member as a hydraulic source of a pressure transmission medium, and by performing combined reversing on valves in the hydraulic control circuit. In this method, a mechanical structure is simplified by using an accumulator, but the on/off number of the accumulator is limited under the limitation of a volume of the accumulator and the affect of a switching mechanism. Due to the limited on-off number, the slide sleeve switch for completion has a single function and a low fault tolerance during operation.
In the Chinese Patent “Hydraulic Slide Sleeve” (Publication No.: CN102278091A), published on Dec. 14, 2011, two preset hydraulic channels are pressurized in sequence by a hydraulic pipeline, hydraulic oil pushes the slide sleeve to open and close to complete the opening, closing or throttling of a production channel in certain reservoir, thereby realizing production control. The hydraulic pipeline used in this method is difficult to achieve multi-stage installation and control, so the construction scale is limited. During the use process of this method, it is necessary to lower a tool to a designated reservoir after the fractured operation is completed, so the operation period is long, and the cost is high.